Head disk interface testers are used in the design and manufacturing of magnetic recording disk drives. Such testers typically include a spindle motor with a removable chuck or clamp that allows a magnetic recording disk to be installed, and an actuator on to which the suspension and magnetic recording head are mounted. The actuator can move the head in a programmed pattern, which may represent a typical seek a pattern during operation of the disk drive, or can maintain the head over a particular region of the disk. The tester is thus able to simulate the operation of the disk drive and enables various mechanical properties of the interface to be determined, including wear of the head and disk, fly height of the slider and "stiction," or static friction which causes the head to stick to the disk. Conventional head disk interface testers use a linear or rotary stepper motor as the actuator. The stepper motor actuator cannot accurately represent the operation of modern disk drives that use a rotary voice coil motor actuator because, unlike actual disk drives, the stepper motor actuator moves in discrete steps and thus represents a relatively jerky motion of the slider across the disk surface. Many modern disk drives use a load/unload ramp located at the other periphery of the disk to support the suspension and head off the disk surface when the disk drive is not operating. The actuator is required to move the suspension up the ramp for loading and down the ramp for unloading with a smooth continuous motion and with a velocity that may vary according to a specific velocity profile. Because of the jerky motion of stepper motors it is difficult for conventional head disk interface testers to precisely simulate the operation of disk drives during the load/unload function.
What is needed is a head-disk interface tester that can accurately simulate the operation of modern disk drives, including providing continuous motion of the sliders over the disk surfaces and up and down load/unload ramps according to various velocity profiles.